add docs

src/main.c

@@ -4,39 +4,51 @@
 #include <string.h>
 #include <stdio.h>
 
+// Use watchdog
 #define WATCHDOG
 
+// UART buffer size
 #define BUFFER_LEN				48
 
+// LED pin info
 #define LED_PIN_DIR				PORT_C.DDR.Pin3
 #define LED_PIN_CR1				PORT_C.CR1.Pin3
 #define LED_PIN_CR2				PORT_C.CR2.Pin3
 #define LED_PIN_OUT				PORT_C.ODR.Pin3
 
+// UART RX pin info
 #define RX_PIN_DIR				PORT_D.DDR.Pin6
 #define RX_PIN_CR1				PORT_D.CR1.Pin6
 #define RX_PIN_CR2				PORT_D.CR2.Pin6
 #define RX_PIN_OUT				PORT_D.ODR.Pin6
 
+// UART TX pin info
 #define TX_PIN_DIR				PORT_D.DDR.Pin5
 #define TX_PIN_CR1				PORT_D.CR1.Pin5
 #define TX_PIN_CR2				PORT_D.CR2.Pin5
 #define TX_PIN_OUT				PORT_D.ODR.Pin5
 
-#define SHORT_PRESS_MS 25
-#define LONG_PRESS_MS 1000
+// Time defines
+#define SHORT_PRESS_MS          25
+#define LONG_PRESS_MS           1000
+#define LED_FADE_TIME           888
 
 // Countdown timestamp (2^15 max, sign used to notify "unitialized")
 volatile i16 countdown_tick = 0;
-
-// volatile u08 exec = 0;
+// Light timer
 volatile i16 timer = 0;
 
+// volatile u08 exec = 0;
 volatile u08 cmd[BUFFER_LEN];
 volatile u08 cmdPos = 0;
 volatile u08 cmdLen = 0;
 volatile u08 state = 0;
+u08 led_state = 0;
 
+/**
+ * Hang processor with big delay and hope for watchdog to kick-in or directly
+ * start watchdog restart by setting counter to 0.
+ */
 void reboot(void) {
 #ifdef WATCHDOG
 	IWATCHDOG.Key = IndependWatchdogReset;
@@ -47,6 +59,9 @@ void reboot(void) {
 	WWDG.Control.Counter = 0;
 }
 
+/**
+ * Start feeding cmd into UART (will process with interrupts)
+ */
 void start_cmd(u08 len) {
 	cmdPos = 0;
 	cmdLen = len;
@@ -84,6 +99,7 @@ i16 elapsed(void) {
 	}
 	u16 next = (TIM1.CounterH << 8) | TIM1.CounterL;
 	if (next < countdown_tick) {
+		// Handle case if timer overflowed
 		return (next + 2500) - countdown_tick;
 	} else {
 		return next - countdown_tick;
@@ -111,14 +127,16 @@ void initialize_state(void) {
 	state++;
 }
 
-#define LED_DELAY 888
-u08 led_state = 0;
+/**
+ * Fade in LED for ticks defined in LED_FADE_TIME
+ * Note: if already turned on - do nothing
+ */
 void turn_on(void) {
 	if (led_state == 1) {
 		return;
 	}
 	led_state = 1;
-	u16 delay = LED_DELAY;
+	u16 delay = LED_FADE_TIME;
 	while (delay > 1) {
 		LED_PIN_OUT ^= 1;
 		delay_tick(delay);
@@ -127,13 +145,17 @@ void turn_on(void) {
 	LED_PIN_OUT = 1;
 }
 
+/**
+ * Fade out LED for ticks defined in LED_FADE_TIME
+ * Note: if already turned of - do nothing
+ */
 void turn_off(void) {
 	if (led_state == 0) {
 		return;
 	}
 	led_state = 0;
 	u16 delay = 1;
-	while (delay < LED_DELAY) {
+	while (delay < LED_FADE_TIME) {
 		LED_PIN_OUT ^= 1;
 		delay_tick(delay);
 		delay++;
@@ -141,18 +163,29 @@ void turn_off(void) {
 	LED_PIN_OUT = 0;
 }
 
+/**
+ * Tick event handler
+ */
 void tick_250ms(void) {
+	// Go trough all initialization states
+	if (state < 2) {
+		initialize_state();
+		// and skip other tasks if not finished
+		return;
+	}
+	// Decrease light timer
 	if (timer > 0) {
 		timer--;
 	}
+	// If we still have time
+	// note: timer can be below zero to work without timer
 	if (timer != 0) {
+		// Keep light on (will do nothing if already enabled)
 		turn_on();
 	} else {
+		// Turn off otherwise
 		turn_off();
 	}
-	if (state < 2) {
-		initialize_state();
-	}
 }
 
 interrupt(IRQ_UART1_RX_F, uart_recv) {
@@ -228,6 +261,7 @@ void main(void) {
 	CLK.SwitchControl.SwitchStartStop = 1;
 	CLK.Divider.Prescaler = 0x00;
 	CLK.Divider.HighSpeedPrescaler = 0x00;
+	// Disable unused peripherals
 	CLK.Peripheral1.I2C= 0;
 	CLK.Peripheral1.SPI = 0;
 	CLK.Peripheral1.Timer2 = 0;
@@ -257,7 +291,7 @@ void main(void) {
 	CLK.Peripheral1.Serial1 = 1;
 
 	// Setup LED pin
-    LED_PIN_DIR = 1;
+	LED_PIN_DIR = 1;
 	LED_PIN_CR1 = 1;
 	LED_PIN_CR2 = 0;
 	LED_PIN_OUT = 1;
@@ -291,22 +325,15 @@ void main(void) {
 	// Start interrupts
 	rim();
 
-	// Fast blink on start
-/*	for (u08 j = 0; j < 10; j++) {
-		LED_PIN_OUT ^= 1;
-		delay_tick(0xffff);
-		IWATCHDOG.Key = IndependWatchdogReset;
-	} */
-
 	// Just for test
 	CFG_GCR |= 0x02; // Set AL for disable main();
 	wfi();
-	
+
 	// Infinite worker loop
-    for (;;) {
+	for (;;) {
 		delay_tick(0xff);
 #ifdef WATCHDOG
 		IWATCHDOG.Key = IndependWatchdogReset;
 #endif
-    }
-}
+	}
+}